1. Field of the Invention
The present invention relates to pressure gauges of the type carried on a vessel being monitored. More particularly, the invention is a mechanical indicator of pneumatic pressure which indicates by color coding whether the pressure being monitored is within specifications. In alternative embodiments, the novel indicator cooperates with or is an integral part of a valve enabling the vessel to be filled with compressed gas. A preferred application is pneumatic tires for transport vehicles. However, the invention is readily applicable to tanks, conduits, and other holders of gases under pressure, and could be employed in any environment wherein internal gas pressure is to be maintained in a predetermined range above atmospheric air pressure.
2. Description of the Prior Art
Pneumatic tires are designed to operate at pressures within narrow predetermined ranges. Typically, tires lose pressure and must be reinflated to specified values by the operator. This maintenance operation requires a pressure gauge. Many operators rely upon service facilities offering compressed air to supply the gauge. If the service facility does not supply a gauge, the operator of the vehicle is obliged to furnish the gauge. It is easy to neglect to bring a tire pressure gauge at all times, and the operator may therefore lack a gauge when desiring to restore or check tire pressure. Even if a pressure gauge is at hand, it is not always convenient to utilize typical tire pressure gauges. Pressure gauges are normally designed to operate when pressed against the valve of the tire sufficiently to release pressure so that it may be measured and indicated. Under conditions of severe temperatures, dust, rain, and other influences, it may prove difficult or unpleasant to check tire pressure.
One answer to this problem is to furnish a pressure gauge which is left in place on the tire, the gauge having an indicator which may be readily viewed to ascertain tire pressure. Such gauges have been proposed in the prior art.
In an indicator shown in U.S. Pat. No. 5,569,849, issued to Craig Cummings on Oct. 29, 1996, a colored liquid flows around a solid member obstructing view of the colored liquid when tire pressure deviates from a predetermined setpoint. Visibility of the colored liquid indicates inadequate pressure. By contrast, in the present invention, a solid colored member aligns with a window formed in the indicator. In the novel indicator, air pressure from the tire acts directly on the solid member. No fluid apart from compressed air contained in the tire is employed.
U.S. Pat. No. 5,103,670, issued to Min-Yu Wu et al. on Apr. 14, 1992, shows an indicator having a bellows operated piston which, when appearing in a window formed in the indicator, aligns with indicia indicating pressure values. By contrast with this approach, the present invention exposes indicia, preferably in the form of a predetermined color, which enables immediate discernment of whether pressure is within specifications. There are no bellows in the present invention.
U.S. Pat. Nos. 5,503,012 and 5,606,123, issued to Masoud Rabizadeh respectively on Apr. 2, 1996, and Feb. 25, 1997, both are based on a ball visible through a window which aligns with indicia. Rabizadeh improves on prior art devices by providing a magnifying glass over the window. However, graduation indicia must still be read in order to determine pressure within the tire. In the present invention, mere discernment of color is required to obtain the same information. There is no magnifying glass required in the present invention.
The subject indicator shown in U.S. Pat. No. 5,641,902, issued to Jung Un Hong on Jun. 24, 1997, incorporates an inflatable member which displays indicia indicating inflation pressure. By contrast, in the present invention, a color signal is visible through a window to indicate tire pressure. There is no inflatable member in the present invention.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.